TrimethylboraneTrimethylborane (TMB) is a toxic, pyrophoric gas with the formula
B(CH3)3 (which can also be written as Me3B, with Me representing
methyl).

Contents

1 Properties
2 Preparation
3 Reactions
4 Use
5 References

Properties[edit]
As a liquid it is colourless. The strongest line in the infrared
spectrum is at 1330 cm−1 followed by lines at 3010 cm−1
and 1185 cm−1.
Its melting point is −161.5 °C, and its boiling point is
−20.2 °C.
Vapour pressure is given by log P = 6.1385 + 1.75 log T − 1393.3/T
− 0.007735 T, where T is temperature in kelvins.[5] Molecular weight
is 55.914. The heat of vapourisation is 25.6 kJ/mol.[4]
Preparation[edit]
TrimethylboraneTrimethylborane was first made by Stock and Zeidler. Their method of
preparation combined boron trichloride gas with dimethylzinc.[5]
Although the substance can be prepared using
Grignard reagentsGrignard reagents the
output is contaminated by unwanted products from the solvent.
TrimethylboraneTrimethylborane can be made on a small scale with a 98% yield by
reacting trimethylaluminium in hexane with boron tribromide in dibutyl
ether as a solvent.[5] Yet other methods are reacting tributyl borate
with trimethylaluminium chloride, or potassium tetrafluoroborate with
trimethylaluminium.[6] Yet another method is to add boron trifluoride
in ether to methyl magnesium iodide.[7]
Reactions[edit]
TrimethylboraneTrimethylborane spontaneously ignites in air if the concentration is
high enough. It burns with a green flame producing soot.[8] Slower
oxidation with oxygen in a solvent or in the gas phase can produce
dimethyltrioxadiboralane, which contains a ring of two boron and three
oxygen atoms. However the major product is
dimethylborylmethylperoxide, which rapidly decomposes to
dimethoxymethylborane.[9]
TrimethylboraneTrimethylborane is a strong Lewis acid. It reacts with water and
chlorine at room temperature. It also reacts with grease but not with
TeflonTeflon or glass.[5]
TrimethylboraneTrimethylborane can form an adduct with ammonia:
(NH3):B(CH3)3.[10]
TrimethylboraneTrimethylborane reacts with diborane to disproportionate to form
monomethyldiborane and dimethyldiborane: (CH3)BH2.BH3 and
(CH3)2BH.BH3.
It reacts as a gas with trimethylphosphine to form a solid Lewis salt
with a heat of formation of −41 kcal per mol. This adduct has a heat
of sublimation of −24.6 kcal/mol. No reaction occurs with
trimethylarsine or trimethylstibine.[7]
MethylMethyl lithium reacting with the
TrimethylboraneTrimethylborane produces a
tetramethylborate salt: LiB(CH3)4.[11] The tetramethylborate ion has a
negative charge and is isoelectronic with neopentane,
tetramethylsilane, and the tetramethylammonium cation.
Use[edit]
TrimethylboraneTrimethylborane has been used as a neutron counter. For this use it
has to be very pure.[10] It is also used in chemical vapour deposition
where boron and carbon need to be deposited together.
References[edit]